Implantable medical devices (IMDs) may perform a variety of functions, including patient monitoring and therapy delivery. In general, it is desirable to design an IMD to be as small as possible, e.g., in terms of volume, footprint, and/or thickness, while still effectively performing its intended function. For example, decreasing the size of an IMD can increase the number of possible locations in which the IMD can be practically implanted. In addition, a smaller IMD can limit the extensiveness of surgery, reduce the likelihood of infection or rejection of the implant, and improve the comfort, and in some cases cosmetic appearance, of a patient after implantation. In other words, a smaller IMD may be more clinically acceptable than a larger IMD.
Examples of IMDs include implantable pulse generators (IPGs) and implantable cardioverter-defibrillators (ICDs). IPGs and ICDs comprise, among other things, a control module, a capacitor, and a battery that are housed in a hermetically sealed container. The battery includes a case, a liner, an electrode assembly, electrolyte, and at least one feedthrough extending through the case that serves as a battery terminal. The liner insulates the electrode assembly from the case. The electrode assembly includes electrodes, an anode and a cathode, with a separator therebetween.